First you may use backtesting. This doesn’t take too much time because you can swiftly scroll thru historical charts attempting to find the signals that would have led you to make a trade if you had been operating your system live at that time.
Backtesting should give you an idea of whether a system has potential. This gives you a good period spread without requiring you to cover 4 entire years. The second way to test forex systems is in a demo account. Here you are dealing with the live market but not using real money. This strategy is slower because you’ve got to wait for your signals to come up in reality. On the other hand, it mimics real live trading strategies with the chance of slippage and other things which are not gong to show up in back testing.
Remember that you can test several systems at the same time in a demo account, provided you keep separate records of their performance. Or you may use several demo accounts. In this way you have a better possibility of ending up with 1 moneymaking system at the end of your period of testing.
Foreign exchange demo accounts also have the edge that you are developing your live trading skills and familiarity with a software platform and charting service at the same time as you are running your tests. This gives you solid real time coaching to prepare you for the moment when you go live with real money. Most foreign exchange brokers will supply free demo accounts which you can use to check forex systems.